Conventional lug loaders or singulators (hereinafter collectively referred to as either lug loaders or singulators) have been found to be inadequate at higher feed speeds. They are also limited in their ability to both singulate and allocate lumber. When lumber is of varying widths and varying in thickness, or bowed, as may be predominant in curve sawing mills, cupped or crooked, and/or skewed on the transfer, it becomes increasingly difficult to handle the lumber at desirable higher speeds.
An example of a conventional lug loader is that taught in U.S. Pat. No. 3,923,142 which issued to Rysti on Dec. 2, 1975. In particular, what is being taught is singulating boards by use of supporting arms rotating around a closed loop, the orientation of the supporting arms controlled by curved deflectors. Pressing arms in opposed radial pairs, are rotatably mounted above the supporting arm to synchronously clamp a board onto a supporting arm. Downstream flow of the mat of boards is arrested by a stop on each supporting arm. Rysti does not disclose a mechanism for straightening lumber which is skewed on the infeed transfer in the lug loader.
Applicants are also aware of U.S. Pat. No. 5,518,106, which issued to Allard on May 21, 1996. Allard discloses using fixed pick-up shoes mounted onto rotating discs for engaging and supporting boards being singulated. Fixed shoes however, have the disadvantage that they may mark the underside of the board as the board is translated over the top of the disc and as the board is released. If a board is finished, for example destined for cabinet making or the like, then any marks from the shoe or overhead clamp will reduce the value of the board. Allard also discloses a speed-up belt to pull the board away from the fixed shoes at the top of the disc to prevent the board from being flipped over as the board is released from the shoes. In some mills the boards have been marked for trimming and grading before the lug loader. Thus if the board has been flipped over by the singulator, as may occur in the case of the Allard device, the board must be flipped back by hand to read the mark. This can be difficult in a high speed application.
Many lug loaders in the prior art, particularly those operating at slower feed speeds, require that, in order to stop the delivery of boards to the singulator, the board mat moving downstream into the singulator device must be pushed back upstream by the stopping means, that is forced away from, for example, the fixed pick-up shoe and clamping device. Worse yet, in some prior art devices the board delivery mechanism must be brought to a complete stop. Both pushing the mat of boards back upstream, and stopping the board delivery mechanism, can be impractical at high speed.
In the prior art applicant is also aware of U.S. Pat. Nos. 5,921,376 and 6,199,683 which issued to Michell et al for, respectively, a High Speed Revolving Lug Loader With Retracting Heel and Hook and a High Speed Revolving Board Singulator With Retracting Shoe and Variable Dwell Duckers, both of which describe the mechanical manipulation of boards to load the boards into individual lug spaces in a lugged outfeed transfer.
Applicant is also aware of the following U.S. Pat. Nos. in the prior art relating to the present invention: U.S. Pat. Nos. 4,077,524; 4,144,976; 4,330,055; 4,638,440; 4,869,360; 5,419,425; 5,662,203; and 5,813,512.